Re: [PATCH] Adjust testcase for O2 vectorization enabling

[Kewen.Lin via Gcc-patches]

Hi Hongtao,

on 2021/10/11 上午10:10, liuhongt via Gcc-patches wrote:
> libgomp/ChangeLog:
> 
>       * testsuite/libgomp.graphite/force-parallel-8.c: Add 
> -fno-tree-vectorize.
> ---
>  libgomp/testsuite/libgomp.graphite/force-parallel-8.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libgomp/testsuite/libgomp.graphite/force-parallel-8.c 
> b/libgomp/testsuite/libgomp.graphite/force-parallel-8.c
> index f9e07039172..0f3d138cebd 100644
> --- a/libgomp/testsuite/libgomp.graphite/force-parallel-8.c
> +++ b/libgomp/testsuite/libgomp.graphite/force-parallel-8.c
> @@ -1,4 +1,4 @@
> -/* { dg-additional-options "-fdisable-tree-thread1 
> -fdisable-tree-vrp-thread1" } */
> +/* { dg-additional-options "-fdisable-tree-thread1 
> -fdisable-tree-vrp-thread1 -fno-tree-vectorize" } */
>  
>  #define N 1500
>  
> 

Thanks for doing this!

This issue was observed in rs6000 specific PR102658 as well.

I've looked into it a bit, it's caused by the "conditional store replacement" 
which
is originally disabled without vectorization as below code.

  /* If either vectorization or if-conversion is disabled then do
     not sink any stores.  */
  if (param_max_stores_to_sink == 0
      || (!flag_tree_loop_vectorize && !flag_tree_slp_vectorize)
      || !flag_tree_loop_if_convert)
    return false;

The new change makes the innermost loop look like

for (int c1 = 0; c1 <= 1499; c1 += 1) {
  if (c1 <= 500) {
     S_10(c0, c1);
  } else {
      S_9(c0, c1);
  }
  S_11(c0, c1);
} 

and can not be splitted as:

for (int c1 = 0; c1 <= 500; c1 += 1)
  S_10(c0, c1);

for (int c1 = 501; c1 <= 1499; c1 += 1)
  S_9(c0, c1);

So instead of disabling vectorization, could we just disable this cs replacement
with parameter "--param max-stores-to-sink=0"?

I tested this proposal on ppc64le, it should work as well.

What do you think of it?

BR,
Kewen